In the processing of wafers used in the manufacture of integrated circuits, it is necessary in various processing steps to accomplish etching of certain areas of the wafer, to remove photoresist coating which may be applied to the wafer, and to otherwise clean the wafer. The use of an acid is required in all of these processing steps.
An example of apparatus which is directed toward these process steps is disclosed in U.S. Pat. No. 3,990 462, to Elftmann et al. As disclosed therein, wafers are disposed in cassettes in turn mounted on a rotary turntable. A central post defines a plurality of pairs of ports, each port positioned to direct fluid therefrom onto an adjacent wafer as that wafer passes due to the rotary motion of the turntable. As disclosed in that patent, one port of each pair carries acid or water, while the other port carries gas, such as gaseous nitrogen, or air. Each pair of ports is positioned so that, with continuous fluid flow from that pair, an atomized fog-type spray is provided to the wafer.
It will readily be understood that processing of such wafers must be done in an extremely even manner, so that all parts of the wafer are processed properly and uniformly. This has been a problem in the type of apparatus disclosed in the above-cited patent. Futhermore, the processing of a wafer in such a system is relatively slow.
In U.S. Pat. No. 3,970,249 to Singer, secondary streams of gas are alternatively applied to a stream of atomized particles by applying those particles to a substrate. The system thereof, however, is not applicable to processing semiconductor wafers, in particular the removal of material from a semiconductor wafer through etching, stripping or cleaning.
Of more general interest in this are U.S. Pat. No. 3,769,992 to Wallestad and U.S. Pat. No. 3,727,620 to Orr.